Jet engines are relatively complex and expensive, and the tests required to determine whether a jet engine is in proper operating condition are correspondingly complex and time-consuming. For example, considering the turbofan type of jet engine, it includes a turbofan section at the input to the engine which is followed by a compressor section, after which fuel is injected and both the turbine driver for the compressor and the turbine driver for the turbofan are powered by the burning fuel. As part of the input turbofan section, there are some non-rotating guide vanes which are individually changed in their angular orientation to optimum values for the particular engine speed, aircraft elevation, and the like. The angle of the non-rotating guide vanes is determined by a "RAM" which has a position determined by the pressure at the output from the compressor. To give some idea of the size of turbofan jet engines, the TF-41 turbofan engine weighs about one and one-half tons and is nearly ten feet long. It has a rated thrust of 15,000 pounds which it delivers at approximately 9,150 revolutions per minute.
Included as part of the controls for a jet engine is the fuel limiting amplifier, which is also known as a temperature limiting amplifier. In practice, when output power from the fuel limiting amplifier is increased, fuel flow to the engine is decreased. The fuel limiting amplifier inhibits the jet engine from operating at such high temperatures and/or stress conditions that the engine will be damaged.
Heretofore, the various tests of the jet engine have been made in a relatively primitive manner, using a stop watch and various individual gauges and instruments. Accordingly, the test results depended to a significant degree on the skill of the tester and the attention given to the testing of the engine by the persons conducting the tests.
Accordingly, a principal object of the present invention is to automate and simplify the test procedures for testing a jet engine, and to make the tests relatively simple and foolproof, so that they may be conducted by less highly skilled and less attentive persons.